In refrigeration appliances, such as vertical freezers and refrigerators combined with a freezing compartment which have, inside a cabinet G, at least one compartment, which is hermetically closed with good sealing and thermically insulated and inside which the temperature is lower than the temperature of the surrounding external environment, there is observed an undesired effect which tends to make difficult the immediate reopening of the door of said refrigeration appliance after it has been opened and closed.
This phenomenon is due to the decrease in the pressure of the air mass admitted to the inside of the refrigerated compartment upon the opening of the door, which is inherent to the decrease in temperature of said air mass after the closing of the door, producing an unbalance between the internal pressure, which is lower, and the external pressure, which is higher.
As a result, a strong vacuum is produced inside the cabinet, resulting in a force on the door acting to keep it closed, and consequently making difficult the immediate reopening thereof. At present, it is recommended that the user wait a few minutes before reopening the door.
In order to overcome this problem and allow users to reopen the cabinet door immediately after its closing and with less effort, a device known as vacuum-breaking valve is used, whose function is to promote the equalization of the internal and external pressures. This valve is comprised of a generally cylindrical and rectilinear tubular body, which crosses one of the walls of the cabinet G of the refrigeration appliance, in order to promote a fluid communication between the inside and the outside thereof and to allow, in certain occasions (notably when the internal pressure is lower than the external pressure), the external air to enter the cabinet, thus increasing the internal pressure until it becomes close to the external pressure, represented by the atmospheric pressure. The tubular body is open on its inner side and has on its outer side a sealing system consisting of a movable seal, which is activated by gravity and is movable between a sealing position when in rest, seated on a valve seat and promoting the sealing of the air passage, and a spaced position, when it is maintained suspended and spaced from the valve seat, due to the difference between the external and internal pressures of the cabinet, thus enabling the air flow to the inside thereof.
The tubular body of the valve may be formed of a thermically conductive material, having its outer end arranged in order to define a heat collector to collect thermal radiation coming from a heat source available in the refrigeration appliance and which can be defined by the compressor. This construction allows the tubular body of the valve to be kept warm enough to prevent ice formation therein, due to the condensation of the air that enters when the valve is open, without interfering with the cooling inside the cabinet. This construction is described in the patent application BR PI0001249-1, of the same applicant.
While operating adequately, mainly when the tubular body of the valve is built of a material with good thermal conductivity and is kept slightly heated, the constructive arrangement of the seal suggested in the prior art uses the force of gravity to keep the seal, in the form of a sphere, seated on the valve seat, sealing the fluid communication between the inside and the outside of the cabinet.
Due to the fact that the seal is gravitationally and vertically displaced between a closed position, seated on the valve seat, and an open position, elevated in relation to the valve seat by action of the pressure difference between the inlet and outlet ends of the tubular body, it should be built in order to be light enough to be suspended by the “vacuum” formed inside the cabinet, particularly when the user starts the movement of reopening the door immediately after a closing thereof.
The construction of the usual spherical seal with a light spherical body is relatively costly and complex, besides allowing surface irregularities, such as barbs, to be formed on the spherical body of the seal. The low weight of these seals and the presence of surface irregularities thereon makes little efficient the closing of the valve seat only by the gravitational seating of a very light and small sphere against the sealing seat of the valve. On the other hand, the use of a heavier seal would make impracticable its upward displacement by pressure difference.
Therefore, in these known solutions, the construction of the seal is determined by the weight limitations, which weight should also be determined so that the valve only opens when the user starts a door reopening, in order to avoid that the presence of the pressure difference after each closing of the door causes the opening of the valve and the admission of external humid air inside the cabinet, even without an immediate reopening of the door. The adequate operation of the valve thus depends on the weight of the seal and the precision of its finishing, even if the limit weight is insufficient to promote an efficient sealing in the closed valve condition.
An inadequate sealing of the valve seat allows the occurrence of a flow of external humid air to the inside of the cabinet any time the internal pressure thereof is lower than the external pressure, causing undue ice formation inside the refrigerated compartment.